Of course you never see the good blizzard mages in 5 man groups. Because those guys are doing it alone or 2 man. I know mages who can solo pretty much every trash pack in every 5 man instance with blizzard. If it's melee and chillable it is killable. It's your own fault if you try to tank a blizzard pull. And you are even dumb if you do this because a good mage will never get hit by melee mobs in his blizzard... And if you taunt and tank the mobs you take pointless damage and ruin the blizzarding. Nothing is more annoying than some idiots spreading, taunting, fearing / whatever your grouped up mob pack that you are blizzarding, trust me. And those are the kind of guys that blame the mage for being "bad" while at the same time running into 10 frostnova'd ghouls/orcs/whatever and cry about being oneshot.
A good mage can literally kite everything that is chillable as long as the group does not вау фекал up. If the group understands the braindead easy concept that you don't need aggro from mobs that will never reach the mage anyways you can help the mage by not trying to play the tank hero and actually do something useful for instance in ubrs the trash around the beast room and the bridge has a few casters that you can pick out of all the melee. A "good" mage can literally solo all of ubrs trash without taking melee damage. The casters can be silenced, the mage can be shielded and healed through.
Don't blame the mage when in truth, you are being dumb for not understanding this game breaking concept.